SubtitleEdit: FixExtraSpaces

public static string FixExtraSpaces(this string s)
{
    if (string.IsNullOrEmpty(s))
    {
        return s;
    }

    const char whiteSpace = ' ';
    var k = -1;
    for (var i = s.Length - 1; i >= 0; i--)
    {
        var ch = s[i];
        if (k < 2)
        {
            if (ch == whiteSpace)
            {
                k = i + 1;
            }
        }
        else if (ch != whiteSpace)
        {
            // only keep white space if it doesn't succeed/precede CRLF
            // 2: when we `if (k - (i + skipCount) >= 1) = > 0`
            var skipCount = (ch == '\n' || ch == '\r') || (k < s.Length && (s[k] == '\n' || s[k] == '\r')) ? 1 : 2;

            // extra space found
            if (k - (i + skipCount) >= 1)
            {
                s = s.Remove(i + 1, k - (i + skipCount));
            }

            // Reset remove length.
            k = -1;
        }
    }

    return s;
}


Note: there is a note that explain why we return 2!